Exhaust Leak at Turbo exhaust pipe connection - What am I dealing with?

[Vincentc]

I was working in the engine room this morning and did something I have not done in a while. I lifted the hatch above the port engine, Covington 671ti, and discovered soot. When I reached down and grasped the Stainless pipe connected to the turbo, I noticed that it was very loose, until I pushed it back into the turbo.



I removed the turbo blanket and discovered that the ring that holds the pipe in place was loose and that the bolt to secure it was broken.




It looks serious and put off enough heat to melt a nearby wire.



I will be wondering and worrying over this until I find out what I am dealing with and what needs to be done to fix it. Your advice over just what needs to be done to fix this correctly will be appreciated. Obviously the ring that secures the pipe to the turbo needs to be replaced. What else will there probably be?

Thanks,

 

[Paul Gwiz]

it looks like the bolt failed, , those turbos put off a lot of heat , I couldn't tell but it looks like you could just replace the bolt . are they connected using a round barrel on both sides of the clamp ends ? A new clamp should do the trick .

 

[Vincentc]

Thanks Paul,

If replacing the clamp is all I need, that would be great. I wonder if there is a gasket between the turbo and the pipe which needs to be replaced?

 

[Genesis]

You're lucky you didn't light the boat on fire; the exhaust coming out of there is at roughly 1000F!

Check the exhaust bracing and make sure you didn't break the clamp due to the pipe coming out the back being improperly braced and exerting enough force to break the clamp. Fix any problems you find there first or you'll just break another one.

Most of the older designs did not use a gasket. Some of the newer setups do. The older ones relied on the flanges being exactly true and undamaged. The problem with leaks like this is that the gas is corrosive and will erode the mating surfaces quite quickly.

The clamp obviously needs to be replaced. But before you just replace it, check the surface of the pipe and turbo outlet and see if it is eroded or not (you need to clean it up first obviously.) A small amount of erosion can be dealt with using Silkolene on the flange area; it's a high-temperature sealant (don't even think about using something like RTV in there!); it's pretty expensive stuff but it's what you want to use. On a VERY thin coating is required; it "cooks" when it gets hot the first time and expands, setting into place and filling small amounts of eroded space. If the flanges are badly pitted or if the Silkolene fails to seal it you're looking at a turbo and/or pipe replacement.

The bad news is that it's very likely soot has been ingested into the engine. The wear that has caused, if it happened, has happened and will shorten the service life of the engine; nothing you can do about that. If the air filter element on the front of that airsep is blackened with soot replace it; you can try cleaning it but you won't be completely effective in getting it all out. If you want to take a crack at cleaning it a cleaner with butyl cellusolve in it will dissolve the soot, but don't get that crap on your hands -- it's nasty stuff -- and make sure you get it all out of the element before you re-oil it. Look at the compressor wheel on the turbos looking down the inlet and see how much build-up you have there as well. There are people who will advise spraying (very lightly!) water down the intake with the engine running to clean compressor wheels; I disagree. Unless the compressor is badly compromised I'd probably leave it alone, assuming the exhaust side is ok and seals back up. If it is badly compromised consider removing the compressor housing (it does come off fairly easily) and manually clean the wheel and housing area -- just make sure you get it all off if you clean any of it, that you don't use anything that could damage the wheel itself and that you pay attention during disassembly and reassembly because if you don't any imbalance or damage to the wheel that occurs has a high probability of grenading the turbo the next time the engine is run. Do not remove the compressor wheel or loosen the nut on the shaft; the exact position of the wheel on the shaft is part of the balancing that was done when it was originally assembled.

Assuming 6-71TIs (what it looks like) the next task is to check the intercooler and see how badly it's plugged up and, if fouled (good chance it is), remove and clean it.

Finally, pull the airbox covers and have a look inside. If you're lucky the airbox is not full of what looks like (and in fact is) oily carbon clumps. If there are some deposits but they're not up to the level of the cylinder ports, LEAVE IT ALONE. If, on the other hand, there are deposits up to the level of the ports or (worse) above that level and in the ports, or if the airbox drains are plugged with crud consideration has to be given to cleaning some or all of it out. This is EXTREMELY tricky to do as if any of that stuff gets loose and into the cylinders or worse, under the compression rings and is trapped between the compression and oil control rings it will act exactly like sandpaper on the cylinder walls. Larger pieces could conceivably get between the piston and cylinder head or valves and be pretty much like a hydrolock with really bad results.

For obvious reasons don't run the boat until you've fixed it -- a fire in the engine room is definitely not on the list of things you want to have happen and you got close.

 

[Vincentc]

Genesis,
Thanks for the detailed and helpful assessment. It is a 671ti.

Interestingly, the plywood crutch support for the port engine exhaust is in place and has not moved. On the other hand, the crutch for the stbd exhaust came loose and had to be reset. No problem with the stbd exhaust so far.

I found replacement clamps online and see there is a 5.25" diameter and a 5.75" diameter clamp listed with no indication which clamp is for which engine. Guess I can measure, and hopefully pick the right spaces to measure.

I respect concerns over a boat fire and wonder if the turbo blanket should be replaced?

Regards,

 

[bobk]

Karl, Is that vacuum limiter on the Airsep housing closed?

Bobk

 

[Genesis]

Closed? You mean closed to airflow? It does flow air when limiting vacuum (when it is pulled open by the vacuum level.) It doesn't look too bad. You can't see the main element on the front of the airsep from the pictures; that's the one to be concerned about.

 

[kelpy]

Do a google search for Silkolene. Get it from a motocross/ motorcycle shop. They sell it for 1/3 the price that a marine exhaust shop asks. It is good stuff.

 

[rsmith]

You are super lucky the boat didn't burn!!! When the 46C's came out the turbo supports were failing. I was on a 46 that caught fire 40 some miles offshore Cape May NJ back in the 70s.We were swimming within 10 minutes of the first indication something was wrong. Oil fed fires are a very bad thing.

 

[captddis]

Since the elbow has seperated from the turbo, you really need to take the elbow off and clean the mating surfaces. I have had problems with silkolene and no longer use it.
MTU makes a silicone type black sealant that will take the heat. Use that on the joint.
Clean the outside of the flanges as well. Any burrs on the outside flanges is hard on the new Marmon clamp. Tap the clamp when tightening to make sure it is seated all the way.

 

[Vincentc]

I agree that i am fortunate there was not a fire.

I believe I now have a pretty good idea about what is involved in fixing things and will start tomorrow inspecting and cleaning, cautiously. I will let you know what I find.

Thanks

 

[Genesis]

To your other question: Soot on the blanket is not a big deal. Oil is as it's a fire risk. If there's any evidence of oil on the blanket material replace it. The blankets also degrade over time due to vibration; the material turns to powder and loses its insulating effectiveness. If the insulation on the inside has become friable (it comes apart when handled) then it's at the end of its service life.

 

[Vincentc]

I spent a few hours this morning cleaning and disassembling.

The Turbo blanket is shot.



but, I believe the Turbo inlet looks OK



The filter element has a pretty good covering of soot.



We have a Lowe's nearby, but no Home Depot. Could not find Zep 505, so I picked up what they had that looked good and also went by O'Riley's Auto Parts for K&N Filter Cleaner and picked up some engine cleaner as well.



Tried all 4 and it seemed to me that Krud Kutter, Greased Lightning and Gunk Engine Cleaner were about equal and and "88 Degreaser a little less equal.

continued - -

 

[Vincentc]

Now for the important finding.

I could only move the collector out about an inch or so from the turbo. The surfaces looked OK to me.



Everything has a coating of Gunk engine cleaner and shines a bit.

The collector slides easily into the turbo,



I hope not too easily, there is about 1/8" of side to side play when the collector is fully inserted into the turbo. In order to get a good look at the surfaces I will have to remove the collector from the hose sleeve attaching it to the exhaust elbow. Does this much play sound like a problem?



Our youngest daughter is home from school and I have committed to take her and some of her friends out on the boat this Friday. I want to fix all that should be dealt with, but if it ain't broke . . .

I am thinking the simplest approach is to cut off the 6" hose connector holding the collector, clean the collector / turbo mating surfaces and buy / order some sealant compound, a new clamp, a new piece of 6" connector hose and some hose clamps Monday morning.

I am wonder just how this will all go back together as there is not a lot of working room with the exhaust pipe crutch limiting movement. Perhaps a new connector hose will slide easily over the collector and elbow pipes. Any suggestion?

I am not clear on the Silkolene sealant. a thin coat probably will not take up a 1/16" gap between the collector surface and the turbo. A sleeve about 1/4" long slides into the turbo. I found an amazing spread on the cost of Silkolene, from $95 to about $200 for a 225 gram tube. My search also revealed an industrial product which looked interesting.

http://www.deaconindustries.com/product-display/deacon-3300

the internet did not give me any reference to an MTU sealeant.

Any experience or thoughts regarding the Deacon industries products

As always, Thanks

 

[Boatnut]

If it were me, I would listen to the guy who does this for a living. There is no better advice than experience talking.
Try calling your local MTU dealer, they probably have the sealant in stock. Considering the damage that a failure in the repair could bring, unless you really know what you are doing, you might consider talking to someone familiar with this repair. 1/4 inch play sounds like a lot, maybe Dave could comment on this. It may just be that that loose fit contributed to the failure in the first place. Heck you have til Friday to take the kids for a cruise, how much trouble is it to remove it and take it to the dealer, or reputable shop and have it checked out?

 

[Vincentc]

Your suggestion regarding calling an MTU dealers is obvious, but something that did not occur to me. I just located the phone number of the nearest dealer and will give them a call tomorrow. Thanks.

I do respect and appreciate the advice of the professionals here who kindly give valuable information.

1/4" play does sound like a lot. Actually I estimate the side to side play at 1/8". The above reference to 1/4" is my estimate of the distance that the sleeve on the collector slides into the turbo.

Just finished spraying a coat of K&N filter cleaner on the filter after I vacuumed it. It removed a lot of the soot. I just applied a second coat of cleaner.

Regards

 

[captddis]

The MTU sealant is "Elastosil N 2189".

 

[Vincentc]

Thanks

 

[SKYCHENEY]

I have not have good experiences with Silkolene either. Cat makes a sealant that works much better than Silkolene. I have not, however, used the MTU product.

 

[Vincentc]

The exhaust is back together and based upon a short run at the dock with a soap and water test, there is no more leak.



We are taking the boat out to the island this afternoon and will give the engine repair a more thorough test.

I replaced the turbo blanket with one I found on ebay. The blanket fits, but looks a little petite compared with the old one. I think I would like something a little more substantial which would provide a little more cover. Any suggestions regarding sources?

There was a fair amount of erosion in the area of the turbo connection



Obtaining the MTU sealant appeared more complicated than a phone call order to JRD who sells an industrial high temp sealant which could be delivered on Wednesday. I chose the phone call. The sealant comes in a caulk tube and is the consistency of caulk. Its description is:

JRD 7100 HI TEMP SEALANT PASTE is a very thick, dense paste that can withstand extremely high temps up to 1700 degrees F. Used in a variety of industries, including Marine Industry, to seal hot gases and solids when using mechanical fasteners. Excellent choice for any combustion engine exhaust application. Available in 4 oz. container, 10.3 oz. caulking tube.

It was easy to apply and filled the gap well. I hope I don't regret experimenting vs taking Captddis kind advice re the MTU sealant.

I was pleasantly surprised with the lack of difficulty putting everything back together. The silicone hose connector was more pliable than the rubber connector that I cut off. Soap and water allowed the hose to slide easily up the connector and I could put the connector in position and then slide the hose down over the exhaust pipe downstream of the connector.

I appreciate all your advice. I will let you know how things work.

Regards